[PATCH][C++] Improve compile-time by ordering expensive checks last

[Richard Biener]

Two cases from a -fsynax-only tramp3d callgrind profile.

Bootstrapped / tested on x86_64-unknown-linux-gnu.

OK for trunk?

Richard.

2019-04-16  Richard Biener  <rguent...@suse.de>

        cp/
        * call.c (null_ptr_cst_p): Order checks according to expensiveness.
        (conversion_null_warnings): Likewise.

Index: gcc/cp/call.c
===================================================================
--- gcc/cp/call.c       (revision 270387)
+++ gcc/cp/call.c       (working copy)
@@ -541,11 +541,11 @@ null_ptr_cst_p (tree t)
       STRIP_ANY_LOCATION_WRAPPER (t);
 
       /* Core issue 903 says only literal 0 is a null pointer constant.  */
-      if (TREE_CODE (type) == INTEGER_TYPE
-         && !char_type_p (type)
-         && TREE_CODE (t) == INTEGER_CST
+      if (TREE_CODE (t) == INTEGER_CST
+         && !TREE_OVERFLOW (t)
+         && TREE_CODE (type) == INTEGER_TYPE
          && integer_zerop (t)
-         && !TREE_OVERFLOW (t))
+         && !char_type_p (type))
        return true;
     }
   else if (CP_INTEGRAL_TYPE_P (type))
@@ -6882,8 +6882,8 @@ conversion_null_warnings (tree totype, t
     }
   /* Handle zero as null pointer warnings for cases other
      than EQ_EXPR and NE_EXPR */
-  else if (null_ptr_cst_p (expr) &&
-          (TYPE_PTR_OR_PTRMEM_P (totype) || NULLPTR_TYPE_P (totype)))
+  else if ((TYPE_PTR_OR_PTRMEM_P (totype) || NULLPTR_TYPE_P (totype))
+          && null_ptr_cst_p (expr))
     {
       location_t loc = get_location_for_expr_unwinding_for_system_header 
(expr);
       maybe_warn_zero_as_null_pointer_constant (expr, loc);